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If I recall correctly, the iPad/iPhone-compiled PNG files had the color channels optimized for the graphics hardware of the devices as well - they wouldn't deco
by mmastrac 5y ago
If I recall correctly, the iPad/iPhone-compiled PNG files had the color channels optimized for the graphics hardware of the devices as well - they wouldn't decode properly anywhere else.
- pornel 5y agoYes, but "optimized" is overselling it. It stored RGBA in a premultiplied form. IMHO it was an unnecessary spec breakage, and a misplaced focus. The most expensive part of decoding PNG is zlib inflate, so any reduction in input data is more important than post-processing savings. If Apple stored app launch images (the feature it's been invented for) as opaque RGB, then colorspace conversion would also be free, and they'd also be saving a quarter of the most expensive stage of decoding. Instead, they've kept the big expensive part big and expensive, and shaved off 3 instructions from the almost free part.